CDNA encoding the type I iodothyronine 5'deiodinase
First Claim
1. An isolated DNA molecule consisting essentially of a DNA segment encoding an enzyme having the activity of Type I iodothyronine 5'"'"'-deiodinase.
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Accused Products
Abstract
The present invention is directed to the cloning, sequencing, and uses of a nucleotide sequence encoding the mammalian enzyme Type I iodothyronine 5'"'"' deiodinase and mutant sequences thereof. This enzyme catalyzes the conversion of thyroxine to triiodothyronine, producing the active form of thyroid hormone. The invention is further directed to the discovery that an untranslated nucleotide sequence is necessary for the recognition of a TGA (termination) codon in the coding region of 5'"'"' deiodinase as encoding selenocysteine, an amino acid essential for the full activity of 5'"'"' deiodinase. The mechanism by which this recognition occurs involves a stem-loop structure in the 3'"'"' untranslated region of the mRNA. The untranslated sequence can be used to incorporate selenocysteine into non-selenocysteine-containing proteins and polypeptides.
21 Citations
15 Claims
- 1. An isolated DNA molecule consisting essentially of a DNA segment encoding an enzyme having the activity of Type I iodothyronine 5'"'"'-deiodinase.
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3. A method of producing a polypeptide containing at least one selenocysteine residue at a desired site, said method comprising:
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(a) preparing an expression vector comprising (i) a first DNA sequence encoding said polypeptide, wherein said first DNA sequence contains a TGA codon at a site corresponding to the desired selenocysteine site in said polypeptide; (ii) a promoter region capable of directing transcription of said first DNA sequence wherein said promoter region is operably linked to the 5'"'"' end of said first DNA sequence; and (iii) a second DNA sequence wherein said second DNA sequence encodes a selenocysteine-insertion sequence and wherein said second sequence is operably linked 3'"'"' to said first DNA sequence and wherein said second DNA sequence is capable of directing the incorporation of selenocysteine into said polypeptide; (b) transforming a host cell culture with said expression vector to obtain a transformed, recombinant host cell; (c) culturing said recombinant host cell under conditions permitting expression and of said protein; and (d) recovering said protein. - View Dependent Claims (4)
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- 5. An isolated reporter gene consisting essentially of a DNA sequence encoding a functional Type I 5'"'"' deiodinase.
- 12. An isolated selenocysteine-insertion sequence which, when operably linked 3'"'"' to a DNA sequence encoding a selenocysteine-containing polypeptide, effects incorporation of selenocysteine into said polypeptide.
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14. An expression vector for the synthesis of a selenocysteine-containing polypeptide, wherein said expression vector comprises:
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(a) a first DNA sequence encoding said selenocysteine-containing polypeptide operably linked to a promoter region; and (b) a second DNA sequence which encodes a selenocysteine-insertion sequence, wherein said second DNA sequence is operably linked to said first DNA sequence and said second DNA sequence directs the incorporation of selenocysteine into said selenocysteine-containing polypeptide, and wherein said second DNA sequence is not translated. - View Dependent Claims (15)
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Specification